From 5495f1f9ea08efd97fc58656267d888913e77d3b Mon Sep 17 00:00:00 2001
From: Tagir Valeev <Tagir.Valeev@jetbrains.com>
Date: Wed, 21 Oct 2020 15:06:59 +0700
Subject: [PATCH] [java-analysis] Do not mark parameter as UNMODIFIABLE_VIEW if
 the method mutability is inferred

Fixes false-positive in RedundantUnmodifiableInspection

GitOrigin-RevId: 82cd0651ea87f62066a8a299ba3d5b572d617ab0
---
 .../codeInspection/dataFlow/Mutability.java   | 19 +++++++++++--------
 .../beforeArgumentOfPureMethod.java           | 10 ++++++++++
 2 files changed, 21 insertions(+), 8 deletions(-)
 create mode 100644 java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/redundantUnmodifiable/beforeArgumentOfPureMethod.java

diff --git a/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/Mutability.java b/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/Mutability.java
index 825b160fa1c3..87336436e633 100644
--- a/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/Mutability.java
+++ b/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/Mutability.java
@@ -126,14 +126,17 @@ public enum Mutability {
       PsiMethod method = ObjectUtils.tryCast(list.getParent(), PsiMethod.class);
       if (method != null) {
         int index = list.getParameterIndex((PsiParameter)owner);
-        MutationSignature signature = MutationSignature.fromMethod(method);
-        if (signature.mutatesArg(index)) {
-          return MUTABLE;
-        } else if (signature.preservesArg(index) &&
-                   PsiTreeUtil.findChildOfAnyType(method.getBody(), PsiLambdaExpression.class, PsiClass.class) == null) {
-          // If method preserves argument, it still may return a lambda which captures an argument and changes it
-          // TODO: more precise check (at least differentiate parameters which are captured by lambdas or not)
-          return UNMODIFIABLE_VIEW;
+        JavaMethodContractUtil.ContractInfo contractInfo = JavaMethodContractUtil.getContractInfo(method);
+        if (contractInfo.isExplicit()) {
+          MutationSignature signature = contractInfo.getMutationSignature();
+          if (signature.mutatesArg(index)) {
+            return MUTABLE;
+          } else if (signature.preservesArg(index) &&
+                     PsiTreeUtil.findChildOfAnyType(method.getBody(), PsiLambdaExpression.class, PsiClass.class) == null) {
+            // If method preserves argument, it still may return a lambda which captures an argument and changes it
+            // TODO: more precise check (at least differentiate parameters which are captured by lambdas or not)
+            return UNMODIFIABLE_VIEW;
+          }
         }
         return UNKNOWN;
       }
diff --git a/java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/redundantUnmodifiable/beforeArgumentOfPureMethod.java b/java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/redundantUnmodifiable/beforeArgumentOfPureMethod.java
new file mode 100644
index 000000000000..4733aaa7fbe8
--- /dev/null
+++ b/java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/redundantUnmodifiable/beforeArgumentOfPureMethod.java
@@ -0,0 +1,10 @@
+// "Fix all 'Redundant usage of unmodifiable collection wrappers' problems in file" "false"
+
+import java.util.*;
+
+class Main {
+
+  static List<String> test(List<String> list) {
+    return Collections.<caret>unmodifiableList(list);
+  }
+}